As far as I know, portions of it are already opened and the rest of the building is under construction. It is 1 block away from the future WTC site.
Here is a markup with approximate location of Park 51. I believe the thin red lines show paths of the wreckage exiting the buildings.
Thank you for posting that, it’s most helpful.
I just read that that is no longer happening and they are doing condos there instead.
Hope it's true.